The Erinnyes (also spelled Erinyes)
were "the Angry Ones", known as the Furies in Roman. They
were the feared avenging goddesses in Greek and Roman mythology who were
born from the falling drops of blood of Uranus (Sky) when he was mutilated
by his son, the Titan Cronus. The drops fell on Mother Earth (Gaea) and impregnated her.

"...and Cronus cut off his father's genitals and threw them into the sea; and from the drops of the flowing
blood were born Furies, to wit, Alecto, Tisiphone, and Megaera."Apollodorus, Library and Epitome (ed. Sir James George Frazer)

Other versions of their birth claim
that they were the daughters of Mother Earth and Darkness, or of Nyx
(Night), or the Titans Cronus and Eurynome (and thus sisters to the Moerae,
the Fates). One of their famous victims, Orestes, gave them the name 'Eumenides',
the 'Solemn Ones', or 'Kindly Ones'. More on Orestes below.

Their home was at the entrance to
Tartarus, that infernal place deep in the Underworld where the souls of
the condemned were exiled, a gloomy place in Hades as far distant from earth as earth is distant from the sky.
Others call their home Erebus, the darkest pit of the Underworld. There, the Erinnyes would screen out those unfortunate doomed who had yet
to atone for their sins, relentlessly tormenting them.

No prayer, no sacrifice, and no tears could move them,
or protect the hapless object of their persecution; and if ever they felt
that the criminal would escape them, they called in the assistance of the
goddess Dike (Justice). The Erinnyes were closely connected to Dike, for the
merciless maintenance of strict
justice was their utmost concern.

What did they look like? Often they
were depicted as repulsive winged female creatures wearing black robes.
Other descriptions adorned them with snakes twined in their hair, piercing
red eyes dripping blood, pitch-black bodies with bat wings, and even sporting
the heads of dogs.

Definitely not a posse you'd want on
your case...

In works of art and on the stage,
however, their fearful appearance was greatly softened down, and they were represented as
solemn and purposeful maidens, wearing the richly adorned attire of huntresses, with a band of
serpents around their heads, and serpents or torches in their hands.

Because nobody really wanted anything
to do with these avenging creatures, mortals rarely referred to the
Erinnyes by name, in case they invoked their wrath. Instead they were
often euphemistically called the aforementioned Eumenides, the 'Kindly
Ones' or 'Solemn Ones', the term coined by their hapless victim called
Orestes.

There were usually said to be three
Furies (note: At Athens there were statues of only two), called Alecto,
Tisiphone and Megaera, but quite often they were depicted as a large flock
of flying creatures, with the three named members leading the avenging
pack. The Harpies, who were filthy, monstrous, vulture-like female beasts
loathed by humans, often served the Erinnyes in capturing or tormenting those
unfortunate people who had displeased them.

Portrayed with and without wings, the
Erinnyes in time became better known as those responsible for avenging
offenses by children against their mothers, and eventually came to be the divine
punishers - along with Zeus - of anyone who committed perjury or patricide
(killing of one's father).

As their influence spread, the Erinnyes
became the personification of the concepts of vindictiveness and
retribution (also see Nemesis),
and represented the psychological torments associated with a guilty conscience.
Eventually their influence extended to the hearing of complaints of
insolence by the young toward the old; punishing disrespect of parents by
their children; as well as lack of hospitality to guests by their hosts, a
terrific breach of ancient etiquette.

Standing and seated Erinnyes
from an ancient Grecian vase

In short, if you messed up, the wicked fury of
the Erinnyes was not far...There were many who incurred the wrath of the
Furies, with catastrophic results. Some of their more famous victims
included Orestes, Oedipus, Alcmaeon, and even the Amazon Queen called
Penthesileia.

What did these perpetrators do to
arouse the anger of the Erinnyes? Orestes murdered his mother and was
relentlessly hounded by the Furies. Eventually Orestes begged Athena for
redemption, going to her temple on the Acropolis of Athens and embracing
her image. After a trial, Orestes was declared not guilty by the Olympian
gods, but the Erinnyes threatened to let fall a drop of their own blood on
earth, which would kill the plants and crops and destroy the people of
Athens if the ruling stood.

Athena convinced the Erinnyes to take
up residence in a grotto at Athens, where they would be worshipped by the
citizens. Bribing them with offers of great honor, Athena was able to
placate their vengeance, and the three named Furies finally agreed to stop
tormenting Orestes. However, some say that the rest of the winged pack of
Furies continued to harass and pursue Orestes, until he finally managed to
appease them by offering a sacrificial black sheep at a place called
Carneia.

A grateful Orestes then named them the
Eumenides ('Solemn Ones', 'Kindly Ones') and dedicated a new sanctuary to
them.

Orestes and the Erinyes,
1875-1893
oil on canvasby Gustave Moreau

What about some of their other victims?

Oedipus
was tortured by the Erinnyes for killing his own father, even though
it was in self defense and Oedipus didn't know that the man he slew on
the road to Cadmus was his dad.

Alcmaeon was punished and chastised
by them for the murder of his mother, Eriphyle, until finally he was driven mad by
the Erinnyes.

Penthesileia, queen of the Amazons,
was haunted for the accidental shooting of her sister, Hippolyte,
killed while out hunting or during the fight following the wedding of
Theseus and Phaedra.

These were but a few of the targets of
their terrible vengeance. People were justifiably terrified of these
timeless crones.

Tisiphone, Alecto and Megaera were
older than Zeus or any of the other Olympians, and were therefore not
quite under the rule of Zeus, though they
honored and esteemed him. They acted on complaints and punished the
transgressors, relentlessly hounding the culprits. Nobody could escape
from their wrath -- they pursued their victims from city to city and
country to country, without rest or pause.

They carried brass-studded scourges in
their hands, inflicting a terrible torment on their victims. Feared and
revered by the ancients, the Furies were mythology's personified avenging
spirits. The sacrifices which were offered to them consisted of black sheep
and nęphalia -- a drink of honey mixed with water. The objects sacred to them
included white turtledoves and the narcissus flower.

A festival called the 'Eumenidia' was
celebrated in their honor at Athens, where they had a sanctuary and a grotto
near the Areopagus. Another sanctuary, with a grove which no one was allowed to
enter lest the Furies' wrath was aroused, existed at
the city of Colonus. They were also worshipped at Megalopolis, where they
were known under the
name of Maniai (Mania).

The Erinnyes, fragment of
Acropolis marbles

Here's some interesting material from
Harry Thurston Peck: The name Erinys, which is the more ancient one, was derived
by the Greeks from the verb erinô or ereunaô, “I hunt down,” or “persecute,” or from the Arcadian word
erinuô, “I am angry”; so that the Erinyes were either the angry goddesses, or the goddesses who hunt or
search for the criminal.

The name Eumenides, which signifies “the
well-meaning,” or “soothed goddesses,” is a mere euphemism, because people dreaded to call these fearful goddesses by their real name; and it
was said to have been first given them after the acquittal of Orestes by the court of the Areopagus, when
the anger of the Erinyes had become soothed. It was by a similar euphemism that at Athens the Erinyes
were called semnai theai, or the Revered Goddesses.